title: The distribution and 'in vivo' phase variation status of haemoglobin receptors in invasive meningococcal serogroup B disease: genotypic and phenotypic analysis.
abstract: Two haemoglobin-binding proteins, HmbR and HpuAB, contribute to iron acquisition by Neisseria meningitidis. These receptors are subject to high frequency, reversible switches in gene expression--phase variation (PV)--due to mutations in homopolymeric (poly-G) repeats present in the open reading frame. The distribution and PV state of these receptors was assessed for a representative collection of isolates from invasive meningococcal disease patients of England, Wales and Northern Ireland. Most of the major clonal complexes had only the HmbR receptor whilst the recently expanding ST-275-centred cluster of the ST-269 clonal complex had both receptors. At least one of the receptors was in an 'ON' configuration in 76.3% of the isolates, a finding that was largely consistent with phenotypic analyses. As PV status may change during isolation and culture of meningococci, a PCR-based protocol was utilised to confirm the expression status of the receptors within contemporaneously acquired clinical specimens (blood/cerebrospinal fluid) from the respective patients. The expression state was confirmed for all isolate/specimen pairs with <15 tract repeats indicating that the PV status of these receptors is stable during isolation. This study therefore establishes a protocol for determining in vivo PV status to aid in determining the contributions of phase variable genes to invasive meningococcal disease. Furthermore, the results of the study support a putative but non-essential role of the meningococcal haemoglobin receptors as virulence factors whilst further highlighting their vaccine candidacy.
authors.affiliation: Public Health England, Manchester, United Kingdom.
authors.forename: Jay
authors.initials: J
authors.lastname: Lucidarme
authors.forename: Jamie
authors.initials: J
authors.lastname: Findlow
authors.forename: Hannah
authors.initials: H
authors.lastname: Chan
authors.forename: Ian M
authors.initials: IM
authors.lastname: Feavers
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Gray
authors.forename: Edward B
authors.initials: EB
authors.lastname: Kaczmarski
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
authors.forename: Xilian
authors.initials: X
authors.lastname: Bai
authors.forename: Ray
authors.initials: R
authors.lastname: Borrow
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Bayliss
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005838:Genotype; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism; D008585:Meningitis, Meningococcal / Q000378:metabolism* / Q000382:microbiology; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D006113:United Kingdom; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D006454:Hemoglobins; C094109:HmbR protein, Neisseria meningitidis; C445303:HpuA protein, Neisseria; C105625:HpuB protein, Neisseria; D011956:Receptors, Cell Surface; D037521:Virulence Factors; D007501:Iron